The purpose of this study is understand the complex interplay between IUGR and placental amino acid transport, in particular that mediated by EAAC1 and CAT1. In order to achieve this goal clear understanding of the membrane distribution and ontogenic regulation of these transport systems is required. Transport activity will be compared to those noted in 1) placenta derived from premature human pregnancies and 2) placenta derived from human infants born IUGR at term. These studies will define ontogenic expression of these transport systems in the presence and absence of IUGR.